Bisfunctional polymers (polymers with functionality at both ends of the polymer chain) are highly valuable materials. If the functionalities are simple functional groups, i.e. acids, alcohols, etc., then these polymers can serve as "macromers", high molecular weight building blocks. If the functionality is present as polymer chains with a different repeat unit, then triblock copolymers are formed. Triblock polymers have physical properties unique to their class of materials. Those consisting of polar/nonpolar components have special adhesion and dyeing capabilities. Triblocks with crystalline/elastic components behave as thermoplastic elastomers, which are rubbery (hence elastomers) yet have only physical crosslinks, allowing them to be melt-processed (hence thermoplastic). This behavior is in contrast to that of most rubber materials in use, which have chemical crosslinks (thermosets), meaning they cannot be flow processed and are not recyclable. Triblock copolymers consisting of poly(methyl methacrylate) (PMMA) and an elastic segment such as a poly(alkyl acrylate) are desirable for such reasons.
It has recently been demonstrated that samarium complexes of the type Cp*.sub.2 SmR (R=hydride, alkyl; Cp*=C.sub.5 Me.sub.5) function as catalysts for the "living" polymerization of methyl methacrylate [Yasuda et al., J. Am. Chem. Soc. 114:4908-4911 (1992)]. Well-controlled polymerizations of acrylates, lactones, and ethylene by these and related lanthanide compounds have also been achieved, leading to the production of block copolymers containing both a polar and nonpolar polymer unit [H. Yasuda et al., Macromolecules 25:5115-5116 (1992)]. The samarium (II) compound Cp*.sub.2 Sm THF.sub.2 (Cp*=C.sub.5 Me.sub.5) has also been shown to exhibit similar behavior, supposedly through a trivalent hydride intermediate; however, relevant literature also documents low (below 50%) initiator efficiency and inflated molecular weights [H. Yasuda et al., Macromol. Chem., Macromol. Symp. 67:187-201 (1993)].
Another recent development in the chemistry of samarium has been the synthesis of a class of Sm(III) complexes formed via bimetallic, two-electron reductions of unsaturated substrates by Cp*.sub.2 Sm and its solvates [see W. J. Evans, J. of Alloys and Compounds 192:205-210 (1993)].
Efforts are continually being made to develop better methods of utilizing new catalysts for polymerizations of and for the production of polymers and triblock copolymers having unique physical properties.
None of the foregoing references is believed to disclose the present invention as claimed and is not presumed to be prior art. The references are offered for the purpose of background information. The contents of these references are hereby incorporated by reference.